As the demand for diesel fuel increases worldwide there is increasing interest in sources other than crude oil for producing diesel fuel. One such source is what has been termed biorenewable sources. These sources include plant oils such as corn, rapeseed, canola and soybean oils and greases such as inedible tallow, yellow and brown greases. The common feature of these sources is that they are composed of triglycerides and Free Fatty Acids (FFA). Both of these compounds contain n-paraffin chains having 10 to 20 carbon atoms. The n-paraffin chains in the tri-glycerides or FFAs can also be mono, di or poly-unsaturated.
There are reports in the art disclosing the production of hydrocarbons from oils. For example, U.S. Pat. No. 4,300,009 discloses the use of crystalline aluminosilicate zeolites to convert plant oils such as corn oil to hydrocarbons such as gasoline and chemicals such as para-xylene. U.S. Pat. No. 4,992,605 discloses the production of hydrocarbon products in the diesel boiling range by hydroprocessing vegetable oils such as canola or sunflower oil. Finally, US 2004/0230085 A1 discloses a process for treating a hydrocarbon component of biological origin by hydrodeoxygenation followed by isomerization.
Applicants have developed a process which comprises a pretreatment step, and one or more steps to hydrogenate, decarboxylate (and/or hydrodeoxygenate) and optionally hydroisomerize the feedstock. The pretreatment step removes contaminants that can poison the downstream catalysts.